20點中一mathz勁easy的~快!

1.
(3b+12)/9=(6b-2)/5
5*(3b+12) = 9*(6b-2)
15b+60 = 54b-18
60+18 = 54b-15b
78 = 39b
b = 78/39
b = 2

2.
(4b-5)/11=(2b+1)/5
5*(4b-5) = 11*(2b+1)
20b-25 = 22b+11
-25-11 = 22b-20b
-36 = 2b
b = -36/2
b = -18

3.
-(7p-3)/5-3p=27
-(7p-3)/5 = 27+3p
-(7p-3) = 5*(27+3p)
-7p+3 = 135+15p
3-135 = 15p+7p
-132 = 22p
p = -132/22
p = -6


4.
係咪應該係 "4p+ (-3p-20)/4=-5" 呀?
4p+ (-3p-20)/4=-5
4p+5 = (3p+20)/4
4*(4p+5) = 3p+20
16p+20 = 3p+20
16p-3p = 20-20
13p = 0
p = 0/13
p = 0



5.
(8r-10)/3=(7r)/4+4
(8r-10)/3 = (7r+4*4)/4
4(8r-10) = 3(7r+16)
32r-40 = 21r+48
32r-21r = 48+40
11r = 88
r = 88/11
r = 8


6.
(22-3r)/2=r/5-6
(22-3r)/2 = (r-6*5)/5
5*(22-3r) = 2*(r-30)
110-15r = 2r-60
110+60 = 2r+15r
170 = 17r
r = 170/17
r = 10


7.
(m+5)/2-(m-6)/9=9
[9*(m+5)-2*(m-6)]/(2*9) = 9
9m+45-2m+12 = 9*18
7m+57 = 162
7m =162-57
7m = 105
m = 105/7
m = 15

8.
-(m+17)/8+(m-4)/5=-3
[-5*(m+17)+8*(m-4)]/(8*5) = -3
-5m-85+8m-32 = -3*40
3m = -120+85+32
3m = -3
m = -3/3
m = -1


9.
(6x+8)/15+(5x-8)/6=14
[6/3*(6x+8)+5*(5x-8)]/(15*6/3) = 14
2*(6x+8)+5*(5x-8) = 14*(15*6/3)
12x+16+25x-40 = 420
12x+25x = 420-16+40
37x = 444
x =444/37
x = 12


10.
(7x-3)/2+(3x-14)/8=-11
[4*(7x-3)+(3x-14)] / 8 = -11
28x-12+3x-14 = -11*8
31x = -88+12+14
31x = -62
x = -62/31
x = -2

1.3b+12/9=6b-2/5
4/3+2/5=3b
26/15=3b
b=26/45
2.4b-5/11=2b+1/5
-5/11-1/5=-2b
-36/55=-2b
b=18/55
3.-(7p-3)/5-3p=27
7p-3=135-81p
88p=138
p=69/44
其他唔做 點解個ans 錯=.=
4.4p+ -3-20/4=-5
5.8r-10/3=7r/4+4
6.22-3r/2=r/5-6
7.m+5/2-m-6/9=9
8.-(m+17)/8+m-4/5=-3
9.6x+8/15+5x-8/6=14
10.7x-3/2+3x-14/8=-11